FA-7576 / Multiplexed protocols / Open access
Quic ack delay is subtracted only up to peer limit · case 01
Quic ack delay is subtracted only up to peer limit.
ROOT CAUSE
The faulty implementation uses `max(0,rtt-delay)` for the quic-ack-delay-is-subtracted-only-up-to-peer-limit decision.
VERIFIED REPAIR
Apply the explicit quic-ack-delay-is-subtracted-only-up-to-peer-limit contract, including the tested boundary and negative cases.
Unsuccessful approach: The attempted repair uses `rtt` and still violates a separate fixture.
Case contract
Bounded offline decision model: quic ack delay is subtracted only up to peer limit. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.
Why this case matters
This deterministic multiplexed protocols model isolates the quic-ack-delay-is-subtracted-only-up-to-peer-limit policy at a network component boundary.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(rtt, delay, maximum):
return max(0,rtt-delay)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(100, 80, 25), 75)", "check('fixture 2', solve(100, 10, 25), 90)", "check('fixture 3', solve(10, 25, 25), 0)", "check('fixture 4', solve(0, 0, 25), 0)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 2 | 90 | 90 | Passed |
| fixture 3 | 0 | 0 | Passed |
| fixture 4 | 0 | 0 | Passed |
| fixture 1 | 20 | 75 | Failed |
SHA-256 / c57ee4ced452c19be1ce40910a8276810df58b053ef2d9d5754732d5cf123bb0
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(rtt, delay, maximum):
return rtt
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(100, 80, 25), 75)", "check('fixture 2', solve(100, 10, 25), 90)", "check('fixture 3', solve(10, 25, 25), 0)", "check('fixture 4', solve(0, 0, 25), 0)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 2 | 100 | 90 | Failed |
| fixture 3 | 10 | 0 | Failed |
| fixture 4 | 0 | 0 | Passed |
| fixture 1 | 100 | 75 | Failed |
SHA-256 / 58b5fb2ae8c3a5728779ea65651899ccfb5103f213a77b6c6033f6c17f15addb
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(rtt, delay, maximum):
return max(0,rtt-min(delay,maximum))
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(100, 80, 25), 75)", "check('fixture 2', solve(100, 10, 25), 90)", "check('fixture 3', solve(10, 25, 25), 0)", "check('fixture 4', solve(0, 0, 25), 0)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 2 | 90 | 90 | Passed |
| fixture 3 | 0 | 0 | Passed |
| fixture 4 | 0 | 0 | Passed |
| fixture 1 | 75 | 75 | Passed |
SHA-256 / fffca33b890c86632d7ae8d5f03eca65248711d5b206f873649430a89b2f32f2
Verification & scope
Bounded deterministic policy model over validated inputs; not a complete protocol stack or an interoperability claim. The five variants rotate the same explicit fixture set. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.
Observations recorded using Python 3.12.14 at 2026-09-29T14:38:13.379871+00:00.
Case digest / 6c1f5773cdab6348b989906a4c46622fe9039740d79dcaf1dbf63cff088126f2